1. Field of the Invention
The present invention relates to an original transporting device capable of effecting exposure while transporting the original.
2. Related Background Art
FIG. 33 is a cross-sectional view showing an example of a sheet transporting device.
In the figure, 1001 is a sheet transporting device main body, disposed at a predetermined position on the top portion of an image processing apparatus. 1002 is a platen glass, 1003 is a transporting belt for transporting the original in an E or D direction by driving a transporting roller 1007. 1004 is an original tray on which the original bundle P is laid. 1005 is a half-moon shaped feeding roller for separating an original on the bottom of the original bundle P laid on the original tray 1004 and delivering it into a transporting passageway.
1006 is an original feeding belt for transporting the original sheet (sheet member), in corporation with the feeding roller 1008, delivered from the original tray 1004 via the transporting passageway toward a direction where the platen glass 1002 is arranged. 1009 is an original exposure portion, scanned at a predetermined speed in an A direction, for leading a reflected image of the original laid on the platen glass 1002 into an imaging system (not shown). 1010 is a large transporting roller which rotates in a forward or reverse direction to turn over the original, or eject the original. 1011 is a paper ejection roller which serves to load the original which has been read on to the original tray 1004 again.
In a device thus constructed, the sheet member from the original tray 1004 is transported from the B end side of the platen glass 1002 into an image reading position, where the sheet is placed in an arbitrary disposition, after which the original exposure portion 1009 of the sheet transporting device main body 1001 is moved in the A direction to read the original, and after completion of reading, the sheet member is ejected from the B end side of the platen glass 1002 and loaded again onto the original tray 1004.
In contrast to an original fixed reading mode, another reading mode referred to as an original flow reading mode has been proposed in which, with the original exposure portion 1009 of the image forming device fixed, the sheet member is transported from the C end side into the other end in the figure to read the original, in order to effect fast image formation without high speed transportation.
However, in the original flow reading mode, there was a problem that in reading the original image, if the time interval to feed the copying paper successively in the main body is sufficient to have the time interval to feed the original successively, the performance of the main body can be completely drawn out, but due to the difference in the kind of the original or the loading amount of originals, or the difference in the environmental conditions, separation of the original from the original tray may be delayed, so that the time interval permissible to feed the original is extended beyond the time interval to feed the copying paper successively in the main body, resulting in a decrease in productivity.